The state has recorded 78 new Covid-19 cases overnight in the 24 hours to 8pm
Ms Berejiklian warned residents they could be carrying virus with no symptoms
Positive results came from 63,000 tests; higher testing rates in the Fairfield LGA
High rates of transmission also detected in Hurstville and Kogarah in city's south
Greater Sydney is now into its fourth week of strict stay-at-home lockdown rules